Complete nucleotide sequence and structural organization of pPB1, a small Lactobacillus plantarum cryptic plasmid that originated by modular exchange

A small cryptic plasmid designated pPB1 was isolated from Lactobacillus plantarum BIFI-38 and its complete 2899 bp nucleotide sequence was determined. Sequence analysis revealed four putative open reading frames. Based on sequence analysis two modules could be identified. First, the replication module consisted of a sequence coding for a replication protein (RepB) and its corresponding target site, and two putative repressor proteins (RepA and RepC). Sequence analysis indicated the possible synthesis of an antisense RNA that might regulate RepB production. A putative laggingstrand initiation site was also found, suggesting that pPB1 replicates via a rolling circle mechanism. The second module of pPB1 consisted of a sequence coding for a putative mobilization protein and its corresponding oriT site. Since the nucleotide sequence of the replication module showed 94.5% identity to the similar region on the Leuconostoc lactis plasmid pCI411, and the nucleotide sequence of the mobilization module had 97.5% identity to L. plantarum plasmid pLB4, it is concluded that pPB1 originated by modular exchange between two such plasmids by homologous recombination. Putative recombination sites where crossover might have taken place were also identifiedThis work was supported by Grant 07G/0035/2003 from the Comunidad de Madrid and RM03-002 from the Instituto Nacional de Investigación y Tecnologı´a Agraria y Alimentaria (INIA). We thank R. Gonza´lez and A.V. Carrascosa for their advice and critical reading of the manuscript. B. de las Rivas was a recipient of a postdoctoral fellowship and A. Marcobal of a predoctoral fellowship both from the Comunidad de Madrid.Peer reviewe

Functional and structural properties of thin electroceramic films by laser radiation

The deposition of single layer electroceramic thin films by pulsed excimer laser radiation (248 nm) on Ti/Pt/Si (111) substrates is investigated as a function af laser parameters (fluence, repetition rate, beam geometry) and processing variables (pressure and composition of processing gas, target-substrate arrangement) under conditions of various temporal and spatial properties of the involves vapor and/or plasma states represented in the type, number, ionization degree, momentum, and energy of the ensemble of species generated. The film characteristics were measured using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, ellipsometry and impendance measurements. The experimental results are related to theoretical results of film growth calculating the densification of the films via momentum trasfer and the temperature of the films via energy storage. The film properties are dicussed in view of suitable permittivities and coupling coefficients for electrical, sensoric and actuatoric applications

Raman spectroscopy on BaTiO3 ferroelectric thin films deposited by a hybrid DC-field enhanced PLD-process

Raman spectroscopy is employed for structural characterization of BaTiO3 ferroelectric thin films, deposited by a hybrid DC-field enhanced pulsed laser deposition (PLD)-process. Pulsed excimer laser radiation (KrF, lambda=248 mn, tau=25 ns) is used for material removal from a sintered BaTiO3-target in an 02 processing gas atmosphere (pressure p(O2)about 1 * 10(exp -1) mbar) with subsequent deposition on a substrate. Additional energy is supplied to the laser-induced plasma via a system of two concentric ring electrodes lying on different electric potentials (difference delta V up to several hundred V), leading to further activation of the plasma and ignition of a DC-discharge in the processing gas atmosphere. Micro-Raman spectroscopy is performed with Ar+ laser radiation (lambda=488 mn), using a microscope unit to achieve a high spatial resolution in the range of 1 gm. The Raman spectra of the BaTiO3 films show peaks typical for the tetragonal/cubic Perovskite structure. Polarization-d ependent measurements reveal a mean c-axis orientation normal to the substrate surface, regardless whether a DC-field is applied or not. Using low DC-bias voltages (delta V=50 V) allows lowering the substrate temperature without affecting the crystal quality of the films, as determined from the full width at half maximum (FWHM) of the Raman peaks, which is a measure for the crystal quality. High DC-bias voltages (delta V=700 V), however, lead to amorphous films. The dielectric constant of the BaTiO3 films is strongly correlated to the crystal quality

Deposition of carbon nitride thin films in a hybrid r.f.-PLD technique

In a hybrid r.f.-PLD technique pulsed laser deposition (PLD) in combination with a capacitively coupled r.f. substrate bias with nitrogen as processing gas was used to synthesize CN(x) films with nitrogen contents up to x=0.31. The r.f. bias leads to the formation of a glow discharge in the processing gas, from which N(2)(+) ions were accelerated onto the growing film owing to the negative d.c. self-bias voltage of the substrate electrode. Ion current densities at the substrate were typically in the order of 30 myA CM(-2). X-ray photoelectron spectroscopy (XPS) measurements on films showed an increasing amount of nitrogen with increasing ion current density and d.c. bias voltage as well as with decreasing substrate temperature. Two different electronic states can be distinguished in the C 1s and N 1s XPS spectra, which can be attributed to an sp2 and sp3 hybridization of carbon in carbon nitride. The corresponding Raman spectra show two features around 1350 cm(-1) and 1550 cm(-1), typi cal for disordered carbon. The incorporation of nitrogen in the films is confirmed by Fourier transform infrared (FTIR) spectroscopy which reveals similar features to those of the Raman spectra, normally forbidden in FTIR spectra. Atomic force microscopy reveals an increasing average roughness and a decreasing microhardness with increasing substrate temperature. With increasing pulse repetition rate the roughness and microhardness increase, saturating for high pulse repetition rates with similar functional dependence

Pulsed laser deposition of crystalline PZT thin films

Sintered targets of PbZ(0.52)Ti(0.48)O3, are used in a pulsed laser deposition (PLD) process to deposit thin ferroelectric films onto a Pt/Ti/Si(111) substrate for electrical applications. Repetition rates vary between 1 and 200 Hz, the deposition temperature ranges from 500-800 deg C. After thin film deposition the films are treated with different post-annealing procedures. The influence of repetition rate, deposition temperature and post-annealing procedures on the morphology, stoichiometry, crystalline phase, and the resulting electrical properties of the deposited films is investigated. Analytical methods used are scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, micro-Raman spectroscopy, and impedance measurements. A model for the dependence of film thickness and stoichiometry on repetition rate and substrate temperature is presented and compared to the experimental results